Riverside Research Institute and the Columbia University College of Physicians and Surgeons will continue their collaborative effort to further develop, refine, and expand advanced clinical methods of ultrasonic tissue characterization for the liver, kidney, and other abdominal organs such as the spleen and pancreas. These advanced methods will stem from current work utilizing digital spectral and cepstral processing methods to assess tissue- characterization parameters such as attenuation. The proposed research will increase the volume of tissue scanned and digitized in each examination. Digitized rf signals will be stored permanently for continuing evaluation as new hypotheses are developed and tested. The tissue-characterization parameters resulting from data processing will be placed in a data base and subjected to statistical analyses to identify optimal examination procedures, processing strategies, and characterization parameters. New parameters are expected to be developed such as spatial variability in attenuation or tissue-element spacing. To take into account the importance of the spatial distribution of tissue-characterization parameters, novel imaging methods will be employed. The large number of patients routinely scanned provides an ample pool of cases for acquiring data on a broad range of clinically significant diseases and for obtaining statistically meaningful results. Engineering research and development will be undertaken by Riverside Research Institute staff members while patient examinations and clinical interpretations will be performed by Columbia University personnel.